URL shorteners have been around forever, but they became considerably more popular as Twitter's popularity grew and users wanted to squeeze as many characters into tweets as possible. You may not have realized, but Twitter now shortens every URL to 19 characters, whether the posted link is greater or less than that number.

To be fair, chances are you click on at least a few shortened links every day, since a lot of publishers (like this one) use them when posting to sites like Twitter and Facebook to track who's clicking links on those sites. But as for personal use: It's tough to see the purpose, unless you're similarly interested in tracking and analyzing how many of your friends click on links you've shared (see, for example, how to check if your emails are being read).